Together with the distal non-glaciated continental basins (especially the Po Plain and the Upper Rhine Graben) and the marine ice-volume records, the sedimentary fillings of overdeepened valleys and basins form important and excellent archives for the understanding of the environmental and glaciation history.
Formation of overdeepened valleys
Overdeepened valleys and basins are commonly found below the present landscape surface in areas formerly affected by glaciations. This includes the European Alps, that were repeatedly glaciated by extensive foreland glaciers during the Pleistocene. An overdeepening is defined as a topographic depression below the fluvial base level that was excavated by glacial processes. Consequently, they act as primary sediment sinks in deglaciating landscapes. After their erosion, overdeepenings rapidly fill up with glacial, lacustrine and deltaic sediments until eventually, they are completely hidden under the modern landscape. The only visible marks in today’s landscape are several deep, elongated lakes that are not yet filled with sediments and that occur along Alpine valleys and its foreland. Lake Constance is, for example, the largest one of those remaining lakes.
A: Non-glaciated landscape characterized by erosion to the fluvial base level.; B: Subglacial erosion during glacial periods may lead to deep excavation below fluvial base level; C: After glaciation, troughs either are filled with sediment or remain unfilled thus forming lakes